This application claims the priority of the commonly owned copending German patent application Ser. No. 100 50 637.2 filed Oct. 12, 2000. The disclosure of the aforesaid priority application, as well as that of each U.S. and foreign patent and/or patent application identified in the specification of the present application, is incorporated herein by reference.
The present invention relates to improvements in power trains, especially in power trains which can be utilized in motor vehicles, and more particularly to improvements in torque transmitting arrangements which can be utilized in a power train for controlled transmission of torque between a driving unit and a driven unit, e.g., between a first machine (such as a combustion engine) and a second machine (such as an electrical machine which can serve as a motor or as a generator). Still more particularly, the instant invention relates to improvements in power trains of the type capable of automatically reversing the direction of torque transmission in response to changes in the direction of rotation of the output member of one of the units and the direction of rotation of the input member of the other unit.
Power trains of the class to which the present invention pertains are disclosed, for example, in commonly owned German patent application Serial No. 199 41 705 (published Mar. 16, 2000). Such power trains are or can be designed to employ at least one freewheel. A drawback of freewheels which are proposed to be employed in power trains of the character disclosed in the published German patent application Serial No. 199 41 705 is that their freewheels are expensive, bulky and heavy, especially when their diameters are large or extra large. Another drawback of conventional power trains employing one or more freewheels is that they tend to generate noise if the parts of the power train (such as the output member of the prime mover) perform vibratory and/or other undesirable stray movements.
An object of the present invention is to provide a power train which employs at least one freewheel and is less expensive than but at least as reliable as similar power trains of presently known construction.
Another object of the invention is to provide novel and improved freewheels for use in the power trains of motor vehicles.
A further object of the instant invention is to provide a power train which is less likely to generate noise than heretofore known and utilized power trains.
An additional object of the invention is to provide a novel and improved connection between the prime mover and one or more electric machines in the power train of a motor vehicle.
Still another object of the invention is to provide a motor vehicle which embodies the above outlined power train.
A further object of our invention is to provide a novel and improved method of operating the above outlined power train.
Another object of this invention is to provide a novel and improved combination of a planetary transmission with one or more flywheels for use in the power train of a motor vehicle.
An additional object of this invention is to provide a novel and improved combination of an infinitely variable transmission and one or more freewheels for use in the power train of a motor vehicle.
Still another object of the invention is to provide a novel and improved transmission which is automatically shiftable in response to changes of the direction of (forward or rearward) movement of a motor vehicle and which embodies one or more freewheels constructed and assembled in a novel and improved way.
The invention is embodied in a power train which can be utilized with advantage in motor vehicles and comprises a variable-speed prime mover machine having a rotary element, at least one electrical machine, and means for transmitting torque between the rotary element of the prime mover machine and the at least one electrical machine. The torque transmitting means comprises a planetary and at least one engageable and disengageable freewheel between the planetary and one of the machines. The at least one freewheel includes an elongated band having a first friction surface engageable with a first complementary surface provided on a rotary component of the planetary or the one machine and a second friction surface engageable with a second complementary surface on a component of the one machine or the planetary. One of the components is rotatable relative to the other component when at least one of the friction surfaces is disengaged from the respective complementary surface.
The prime mover machine can include an internal combustion engine and the rotary element can constitute a shaft (such as a crankshaft) of the engine. The at least one electrical machine can be arranged to start the engine during a first stage of operation of the power train, and the engine is or can be arranged to drive the at least one electrical machine during a second stage of operation of the power train. The at least one electrical machine can constitute a generator which is arranged to convert mechanical energy into electrical energy at least during the second stage of operation of the power train.
The planetary comprises or can comprise a rotary sun gear member, a planet carrier member, at least one planet pinion member which is rotatably journalled in the carrier member and mates with the sun gear member, and an internal gear member which mates with the at least one pinion member. A portion of the band can be fixedly connected to one of the aforementioned members forming part of the planetary. The torque transmitting means can further comprise a second freewheel which is operable to transmit torque between two members of the planetary. The at least one freewheel can be assembled to be operable to transmit torque between a member of the planetary and a housing of the prime mover machine.
The at least one freewheel can be constructed, assembled and installed for an operation such that it transmits torque between the rotary element of the prime mover machine and a member of the planetary, an a second freewheel of the torque transmitting means can be actuated to transmit torque between a member of the planetary and the at least one electrical machine. Alternatively, the at least one freewheel can be arranged to transmit torque between the sun gear member and the planet carrier member, and the torque transmitting means of such power train can further comprise a second freewheel which is operable to transmit torque between the internal gear member and a housing of the prime mover machine.
The band can include a friction lining and one of the aforementioned friction surfaces is then provided on such friction lining. The friction lining can be of one piece and can extend lengthwise of the band; alternatively, the friction lining can include a plurality of discrete sections which are spaced apart from each other lengthwise and/or transversely of the band.
It is also possible to provide the at least one freewheel with a layer of slippage promoting agent which is applied to one of the two friction surfaces of the band. As already mentioned hereinabove, the band can include a friction lining, and the other of the friction surfaces is then provided on such friction lining.
The slippage promoting agent can contain a plastic material, e.g., a fluorpolymer.
The band can be installed in tensioned condition and is or can be out of contact with one of the complementary surfaces in the disengaged condition of the freewheel.
The band can be arranged to become disengaged from one of the complementary surfaces under the action of centrifugal force; alternatively, or in addition to the ability of the band to become disengaged from the adjacent complementary surface under the action of centrifugal force, the means for changing the condition of the freewheel can include an electromagnet.
If the torque transmitting means of the improved power train further includes a second freewheel which is arranged to operate counter to the at least one freewheel, the two freewheels can have a switching point at a predetermined rotational speed of the output element. One of the freewheels can be disposed in a power flow between the sun gear and the planet carrier of the planetary; the other freewheel is then disposed between the internal gear of the planetary and a housing of the prime mover machine.
The improved power train can further include at least one flywheel, e.g., a flywheel which is affixed to the rotary element of the prime mover machine.
The novel features which are considered as being characteristic of the invention are set forth in particular in the appended claims. The improved power train itself, however, both as to its construction and the modes of assembing and operating the same, together with numerous additional important features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.
FIG. 1 is a perspective view of the band of a pull-type freewheel which can be utilized in the torque transmitting system of the improved power train;
FIG. 2 is a similar perspective view of a push-type freewheel;
FIG. 3 is a partly diagrammatic and partly axial sectional view of a power train which embodies one form of the invention and employs a planetary transmission, a centrifugal force-operated pull-type freewheel and a centrifugal force-operated push type freewheel; and
FIG. 4 is a similar view of a modified power train with shiftable freewheels.